The present invention relates to a method for weaving pile fabrics having at least two different pile heights in a same pile row in a weaving machine of the gripper-Axminster type, comprising at least two pile yarn carriers separately driven to select, according to a pattern to be woven, of one or several pile yarns being presented, in a position selected, to a gripper driven by an oscillating gripper shaft, provided to draw the selected pile yarn off throughout a length desired, by rotating the gripper shaft, the said weaving machine furthermore comprising a cutting device to cut through the pile yarn selected after the selection and this pile yarn being inserted into the fabric, after the pile warp yarn having been cut. The present invention also relates to pile fabrics made according to such a method on gripper-Axminster weaving machines provided for such a method to be applied.
The pile yarn carriers are provided on a carrier system and are controlled by a Jacquard machine in order to present the pile yarns required, in accordance with the pattern to be woven, to the grippers (which are supported by a gripper shaft). The grippers are clamping the pile yarns selected, after which the device will perform a relative motion between the grippers and the carrier system until the yarns selected will have been drawn off throughout the length required. The cutting device will cut at the level of the pile yarn carriers, so that one part of the pile yarns will remain clamped in the grippers, and the other part of the pile yarns will remain clamped in the pile yarn carriers. The part of the pile yarns picked up by the grippers, will be inserted into the backing fabric by rotating the gripper shaft for weaving it in as a pile.
A strong tendency is observed to realize the pile fabrics having various structures within the same fabric. Not only with face-to-face weaving but also when weaving single fabrics, this tendency to realize various structures in a fabric is known. A variable pile height is one of the aspects for which weaving single fabrics is especially suitable, i.e. one pile in the fabric will have a pile height different from the other pile. In practice, with Axminster weaving this may mean:                the pile height of the pile in one pile row is different from the pile height in a next pile row (by pile row is meant the total amount of pile yarns which are simultaneously inserted into the fabric by the grippers, installed on a gripper shaft, is used in the fabric);        the pile height of the pile within one pile row is different from pile to pile;        the pile height within the fabric will be varying between two or several heights;        the pile used of a different height, will be all U-tufts or one pile level one pile level is U-tuft and the other pile levels are J-tufts (U-tuft is meaning that the two pile legs of the pile burl, after having been inserted into the fabric, will have the same length; J-tuft is meaning that the two pile legs of the pile burl after having been inserted into the fabric, will have a different length);        all pile yarns will be suitable for the different pile heights or each pile yarn may only be used for one pile height.        
From the state-of-the-art, already different solutions are known to realize different pile heights within one pile row. Thus, the American patent publications U.S. Pat. Nos. 3,963,057 and 3,963,058 are describing a manner in which, in one same pile row, several pile heights are used, by selecting all the pile yarns to be used in one pile row by bringing the pile yarn carriers into their exact position near the grippers. Thereafter, the grippers will take the pile yarns and will move the pile yarn carriers, supporting the pile yarn for which a higher pile height is required, away from the grippers in the direction of the pile yarn cutting device. Then the cutting device will present itself, which is provided with a finger pointing forward throughout the entire length of the cutting device in order to push forward the pile yarns destined to form a longer pile, towards the grippers, so that these pile yarns will be drawn off the carriers throughout a greater length, after which in the pile row, pile yarns may occur having both lengths which will be cut simultaneously by the cutting system.
However, this method has the disadvantage that the fingers provided on the cutting device (which have to draw the pile yarns further off the carrier) are pushing against the yarn at an unfavourable angle. Due to this, the yarn and the carrier will be subjected to an excessively loading. Cutting long pile yarns also will occur at an unfavourable angle, so that the pile height obtained will be inexact and the cut imperfect.
In U.S. Pat. No. 3,963,057 there are two selection elements per pile warp carrier available for that purpose: one to select the pile yarn desired and one to indicate whether the pile yarn in question should be carried out having a longer pile or not. Double the number of selection elements will render the device according to U.S. Pat. No. 3,963,057 very expensive and large.
In U.S. Pat. No. 3,963,058 the shape of the carrier will determine which pile yarn will be selected having a higher pile and which not. This method has the disadvantage that each yarn is destined to form a high pile or a low one, which will strongly restrict the possibilities to form a pattern.
The British patent publication GB 2145121 is likewise describing a device to use pile yarns having a different length within a pile row. Enabling to select, per pile warp carrier (the machine being at rest), which pile yarn may be used for the high pile and which for the low pile, which still means a serious restriction of the possibilities to form patterns. Furthermore, the device is functioning as follows: the pile yarn carriers will present the pile yarns selected to the grippers, which will grip the pile yarns selected. By moving the carrier system, the pile yarns are made to length for the short pile. The pile yarn carriers being adjusted for pile yarns having a short pile, are kept in position, while the pile yarns for the pile yarns destined for the long pile will be brought out of reach of the cutting device. When the cutting device will subsequently proceed to cut, only the pile yarns destined to become short pile are cut through. Subsequently, a cam control will bring the pile yarns to form the long pile back into its position selected, whereupon the pile yarn grippers will realize an additional motion in order to draw the pile yarns off the pile yarn carriers throughout the additional pile length, in order to form the long pile. Then again the cutting knife will carry out a cutting motion. This method has the disadvantage that both the motion of the pile yarn carrier will be controlled by two drives (normal selection and cam control for dividing pile yarns into a short and a long pile) and also the motion to produce pile length (so called draw off) will occur by two drive systems (motion of the carrier system and motion of the gripper).
In the European patent publications EP 1375513 and EP 1375713 an Axminster-Jacquard machine is described, in which each pile yarn carrier is driven by a separate motor to move towards one of the pre-defined positions, the carrier transmitting to the gripper a selected pile yarn or one or several carriers taking up a position to check whether it is positioned correctly.
The purpose of the invention exists in finding a solution to obtain a fabric with several pile heights within a pile row by means of a weaving machine of the gripper-Axminster type, while the pile heights realized within a pile row, may be different from the pile heights realized in other pile rows and where all pile yarns may be used for all pile heights without any restriction. It is a further purpose to attain this by means of a limited number of driving means.